I don’t find these to be cliches so much as literary devices to avoid having a 50,000 page book with the complex background of entire world(s). They are simplifications that allow a story to be told. Shall we throw out all theater that has simplified backdrops? Asimov once wrote that there were two reasons he used the human-only Galactic Empire. The first reason was to avoid conflicts with John Campbell, who Asimov felt would impose racist overtones to the stories (i.e., humans are better than aliens being a metaphor that people of northern European extraction were better than everyone else). The second reason was to simplify the stories. Because he was dealing with human society with his psychohistory, he felt aliens would complicate things too much. Ignoring relativistic time problems and using ftl also make a story tellable, unless you’re telling a story specifically involving those.
It all depends on what the author is focusing on. Different authors do reality differently.
My two dollars (due to inflation).
